The present invention relates to a gas expansion silencer of the type comprising a tubular endpiece for connection to a supply of gas under pressure flowing subsonically, and a low-pressure stage connected to the endpiece via sonic flow holes for the gas and comprising, at its end opposite from the endpiece, orifices for gas outlet at subsonic speed, said low-pressure stage being filled entirely with porous metal packing.
Such a silencer is described in document EP-A-0 404 801 and is usable as an injector or an ejector for expanding a gas, in particular in a blower device comprising a series of such silencers fed with hot air for defrosting the air inlet filters of large compressors or large gas turbines. It enables the noise that would be produced by the direct sonic expansion to the free atmosphere for a given hot air outlet section to be attenuated by about 25 decibels (dB) to 45 dB, and presents numerous advantages compared with the competing devices of the prior art, as described in above-specified document EP-A-0 404 801 to which reference can be made where necessary, and the content of which is incorporated herein by reference.
An object of the present invention is to improve that silencer, enabling its efficiency and its performance to be further improved.